specs: bench bodies Zig never type-checks (8 specs reject once referenced) #6268

Problem

Zig analyses a function lazily. A bench body that t27c gen emits is never referenced by a test, so zig test never type-checks it. The bench lane (#6258) referenced every bench with _ = &bench_x; and found that in 8 specs that pass the reference path, Zig rejects the bench body:

• value of type 'u32' ignored (a call result dropped as a statement), in fpga/boards/arty_a7_integration, fpga/boards/qmtech_a100t_integration and fpga/testbench/{cts,partition,power,simulator,router}_tb. Example: estimate_latency(...) in bench_cts.
• unable to resolve comptime value in isa/ternary_gates (a .{...} tuple indexed with a runtime value).

From the same run: 78 of the 116 former-BenchBlock files fail once their benches are referenced, and fpga/testbench/gf16_accel_tb hangs in test_add_zero.

Goal

Every bench body in specs/ type-checks, and a check keeps it that way.

Original checks (kept for history; the Queen does not run these)

• The 8 specs above compile with every bench referenced (_ = &bench_x; or an equivalent t27c option).
• Either t27c gen emits a reference to each bench, or a CI check compiles the bench bodies. Whichever is chosen is written down in the PR.
• The 78-file figure is re-measured and either fixed or listed in a ledger.

Original file list

Spec fixes under specs/, plus t27c's zig backend if the chosen fix is to emit a reference. t27b does not change: it already lowers and compiles each bench body (#6258).

Refs #6063

Queen-runnable restatement (2026-10-05)

The first attempt (branch queen-6268) left no diff against master. Re-measured on master 13e212a by generating each spec, appending test { _ = &bench_x; } for every bench and running zig test --test-no-exec: all 8 specs are still rejected (7 with value of type 'u32' ignored, isa/ternary_gates with unable to resolve comptime value at the bench bodies that are written in Zig syntax - @setEvalBranchQuota, @intCast, for (0..1000)). A spec-only fix is measured to work: writing the dropped call as _ = estimate_latency(...); in cts_tb.t27 removes that error. This restatement covers the spec fixes; the generator option and the CI check from the original goal are hand-written Rust/YAML and are not part of this card.

Boundary

• specs/fpga/boards/arty_a7_integration.t27
• specs/fpga/boards/qmtech_a100t_integration.t27
• specs/fpga/testbench/cts_tb.t27
• specs/fpga/testbench/partition_tb.t27
• specs/fpga/testbench/power_tb.t27
• specs/fpga/testbench/simulator_tb.t27
• specs/fpga/testbench/router_tb.t27
• specs/isa/ternary_gates.t27

User Scenarios & Testing

• Given master, where each listed spec's bench body is rejected by Zig once the bench is referenced, when every dropped call result in a bench is written as _ = call(...); and the ternary_gates benches are rewritten in t27 constructs (no @ builtins, no for (0..n), the operand array indexed by a value the language defines), then zig test accepts each spec with every bench referenced.
• Given the fixed specs, when t27c test-report runs them, then their existing tests still pass.

Requirements

• FR-001: The change MUST make every bench body in the 8 listed specs type-check when referenced, by editing the bench bodies only.
• FR-002: The change MUST NOT change test blocks or function bodies, and MUST keep every bench (no deletion of a bench to silence it).
• FR-003: The change MUST NOT add or modify non-t27 hand-written code (specs/policy/own_language.t27); bootstrap/ and .github/ are out of scope.

Success Criteria

• grep -cE '^ +_ = ' specs/fpga/boards/arty_a7_integration.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/boards/qmtech_a100t_integration.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/testbench/cts_tb.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/testbench/partition_tb.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/testbench/power_tb.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/testbench/simulator_tb.t27 prints at least 1
• grep -cE '^ +_ = ' specs/fpga/testbench/router_tb.t27 prints at least 1
• grep -c '@' specs/isa/ternary_gates.t27 prints 0
• t27c test-report specs/fpga/testbench/cts_tb.t27 | grep -cE '^ FAIL +0$' prints 1
• t27c parse specs/isa/ternary_gates.t27 exits 0 and the spec has at least 2 tests.